1. Field
The field hereof relates to the extraction of substances, and in particular the extraction of phosphate and oil from algae and their water environment.
2. Prior Art
The following is a list of some prior art that presently appears relevant:
U.S. Pat. No. Kind Issue or Patentee or or Pub. Nr.CodePub. DateApplicant4,023,734B1May 17, 1977Herve et al.4,897,266B1Jan. 30, 1990Herve et al.6,346,252B1Feb. 12, 2002Moigne7,311,838B2Dec. 25, 2007Herold et al.7,419,596B2Sep. 02, 2008Dueppen et al.7,431,841B2Oct. 07, 2008Herold et al.7,431,952B2Oct. 07, 2008Bijl et al.7,435,707B2Oct. 14, 2008Langer et al.7,435,715B2Oct. 14, 2008Broeckx et al.7,439,034B2Oct. 21, 2008Weiner et al.    Non-Patent Literature: U.S. Dept. of Energy, Natl. Algal Biofuels Tech. Roadmap, (June, 2009).
Phosphorus, a multivalent nonmetal of the nitrogen group, is essential to all life forms. It is essential for the structure of every cell and many biological functions. It is allotropic, i.e., it is capable of existing in two or more distinct forms.
Phosphorus is an integral part of most fertilizers. Concentrated phosphoric acids are used in fertilizers for agriculture and farm production. Fertilizer phosphorus is now primarily derived from phosphorus rocks processed with ammonium nitrate and sulfur. Recovery costs are dependent upon sulfur prices (an oil production byproduct), ammonium nitrate (made with natural gas), and the increased cost to process the decreasing quality of available ore. Since many conditions limit the discovery and exploitation of new sources, it is very desirable that fertilizer makers be able to recover phosphates from local ecosystems for reuse.
In the natural world phosphorous is too active to exist in its pure or elemental form, but only in the form of phosphates, which consists of a phosphorous atom bonded to four oxygen atoms. Phosphates can exist as the negatively charged phosphate ion, which is how they occur in minerals, or as organophosphates in which there are organic molecules attached to one, two, or three of the oxygen atoms. Phosphates can be found in ponds, lakes, and rivers.
Phosphorus moves within the environment mainly through soil, water, and living organisms. Plants absorb and incorporate phosphates from soil. The plants are consumed by herbivores, which are in turn consumed by carnivores. When the carnivores die, their decay returns phosphates to the soil and the process repeats. The movement of phosphorus through the environment is called the phosphorus cycle.
The constant addition of phosphates to the environment by humans conducting agricultural activities causes their concentrations to exceed natural levels, so the phosphorous cycle is strongly disrupted. Phosphorous concentrations have thus been increasing in surface waters, raising the growth of phosphate-dependent organisms, such as algae and duckweed. These organisms use great amounts of oxygen and restrict sunlight from entering the water. This affects the growth cycle of other organisms. The process by which bodies of water become enriched in dissolved nutrients is known as eutrophication; the nutrients stimulate the growth of algae and other plant life and thereby deplete the amount of dissolved oxygen in the water.
The removal of anything from an ecosystem's water is a delicate art. The basic ecological relationships are typically complex. If too much or too little of anything is removed, it can cause a critically deleterious situation. For ecological maintenance ecologists therefore desire to keep phosphorus levels under control in water environments to maintain a natural habitat, while at the same time recovering the excess for other uses. Careful attention is required to leave the originating water environment safe.
Fish excrete phosphorous in their waste materials but the phosphorus can be taken up in part by the plant life and remain in the ecosystem. Excess amounts of phosphorous that would have degraded the environment can be taken up instead by the use of ferric oxide media, which has been shown to remove phosphate from water in a safe, consistent, and repeatable fashion. It is used in aquariums, for example. Typically, in an aquarium setting, after saturation by phosphorus, ferric oxide media is added to collect the excess phosphorus, whereafter the iron particles are removed, discarded, and replaced with new materials.
Ferric oxide media are known by a number of names, including ferric oxide, ferric iron, hematite, red iron oxide, synthetic maghemite, or simply rust. Rust is a general term for a series of iron oxides, usually red oxides, formed by the reaction of iron and oxygen in the presence of water or air moisture. Several forms of rust are distinguishable visually and by spectroscopy, and form under different circumstances including hydrated iron(III) oxides Fe2O3.H2O and iron(III) oxide-hydroxide (FeO(OH), Fe(OH)3).
In settings other than aquaria, the water containing excess phosphorus is urged to flow through a container and to come into contact with the rust surfaces suspended within it. The surfaces are positioned as baffles. The baffle sheets are sized to equivalently match approximately one gram of rust for each 3.8 liters (1 gallon) of water in the container over a production cycle. The orthophosphate levels in the water can be measured using an appropriate instrument both before and after exposure to rust to help estimate the size of the surfaces necessary in a particular ecological setting. In practice, phosphate levels are measured at the start, and then hourly until levels fail to decline further, which may be in as little as two hours, depending upon water pH and temperature.
Green looking pond water is caused by an excessively large number of phytoplankton, which are part of the algae family that has thousands of distinct species. The algae are distributed worldwide in the sea, in freshwater and in damp situations on land. Algae represent a large group of different organisms from different taxonomic divisions. In general, algae can be referred to as plant-like organisms that are usually photosynthetic and aquatic, but do not have true roots, stems, leaves, or vascular tissue, and have simple reproductive structures. The algae have chlorophyll and can manufacture their own food through the process of photosynthesis. In turn, the algae can be processed to harvest their various components for making fuels and various other useful compounds. These organisms are often very small, with the most common ones found in ponds being around 15 microns in diameter. Algae this small are best processed as described in the above copending '380 application. Algae larger than this are more amenable to bulk processing by the method described below, although the smaller micro-algae will also be processed.
The cell walls of algae are generally the same as those of plants. Different plants have slightly different chemical makeups in their cell walls. A rigid layer of cellulose strengthens the cell and provides structural support. One interesting organic component of the cellulose is lignin, a complex aromatic polymer that provides the primary strength of the cell wall. The cell wall protects the very thin, highly flexible, but structurally weak cytoplasm membrane that lies under the wall and surrounds the interior of the cell.
The cell interior, the cytoplasm, consists of a solution of salts, sugars, amino acids, vitamins, and a wide variety of other soluble materials in water. Since the cytoplasm has a higher solute concentration than the water surrounding the cell, osmosis causes water to pass from outside the cell through the relatively permeable cell wall, continue through the cytoplasm membrane, and dilute the cytoplasm. This builds up pressure within the cell until it equalizes to the effective osmotic pressure and, if not for the rigidity of the cell wall, the cell would burst. Other chemical compounds necessary for the life of the cell are selectively passed through this membrane and waste products are evacuated through it. There are gasses that enter, such as nitrogen, and those that leave, such as oxygen. It is because of the gases in respiration, and the lipids to store energy, that the healthiest of the microscopic algae are normally found at the top layer of the pond water.